ARM C code

#include <stdio.h>

#pragma GCC push_options
#pragma GCC optimize("Og")

int func(void) {
    register int R0 asm ("r0") = 1;
    register int R1 asm ("r1") = 0xC;
    register int R2 asm ("r2") = 0;
    register int R3 asm ("r3") = 0;

    while (R1 != 0) {
        if ((R1 & 1) != 0) {
            R2 += R0;
        }
        R0 <<= 1;
        R1 >>= 1;
    }

    return R2;
}

int main(void) {
    register int result = func();
    printf("R2 = 0x%X\n", result);
    return 0;
}

#pragma GCC pop_options